This invention relates to clutches and clutch systems for transferring torque from an engine to a transmission system and more particularly relates to a clutch system for use in vehicles, e.g. in automobiles and trucks.
Most such systems are single clutch systems, i.e. a single clutch is either engaged or disengaged to cause transfer of essentially all torque from an engine to drive wheels when the clutch is closed or none of it when the clutch is open. Such systems have had serious disadvantages since the engine becomes entirely disengaged from the drive wheels when shifting occurs within a transmission between the clutch and the drive wheels. Completely smooth transition between various transmission gears is thus not possible.
Transmissions are known having dual input shafts from the engine and it has been known that automatic dual clutch systems could be used to transfer torque from an engine through such a transmission to drive wheels while permitting shifting of gears for varying torque transfer without complete engine disengagement. Such an automatic system is, for example described in U.S. Pat. No. 6,819,997, incorporated herein by reference. Such known systems, nevertheless have had serious disadvantages.
Although mechanical actuators are mentioned, U.S. Pat. No. 6,819,997 primarily relies upon hydraulically operated actuators. No structure or suggestion of how mechanical actuators might be made to function is disclosed or suggested in U.S. Pat. No. 6,819,997. Furthermore, this patent discloses nothing as to how adverse effects of wear and overheating, due to friction between clutch surfaces during torque transfer changes, might be reduced. There is certainly no disclosure or suggestion as to how spacing between friction surfaces might be controlled or maintained.
Commonly assigned U.S. Patent publication US 2005/0139442, filed Dec. 23, 2004 and published Jun. 30, 2005, incorporated herein by reference, describes a dual clutch transmission system having two transmission input shafts and one transmission output shaft where each transmission input shaft is connectable to an internal combustion engine via a clutch of a torque transmission device. Friction clutches are described. A problem with the systems described in this patent publication is that there is no disclosure or suggestion of desired clutch friction plate spacings and certainly no discussion or suggestion of how to avoid significant variability between friction plate spacing yielding clutch packs that are either too tight causing significant wear and heat at friction surfaces or are too loose causing slippage and/or requiring significant mechanical travel before engagement can occur. Extreme variability within such dual clutch apparatus and between such different apparatus can thus be common, making fitting into assembly line operation extremely difficult and frequently unacceptable and causing undesirable variability between resulting products.